The present invention relates to a method employing an apparatus in conjunction with a hammer-drill to penetrate thick metal and rebar encountered during concrete, rock or masonry boring operations (hereafter referred to as “rock drilling”) without requiring a change in drill equipment. Hammer-drills are recognized as the most efficient way to bore into concrete, rock, or masonry (hereafter collectively referred to as “rock”) and are employed when the primary task is to penetrate such materials. By employing the present invention, operators are relieved of the necessity of carrying an additional drill or other equipment in order to address metal should any be encountered during rock drilling. Such an advantage will be particularly beneficial in situations where the transportation of a second drill, or other equipment, would be undesirable. The additional weight of a second drill, or other equipment, would be particularly undesirable in certain military operations or other operations in an austere environment.
On occasion, during rock drilling, metal plate or other inorganic materials are encountered, often unexpectedly, embedded in the rock. Neither the equipment nor bits in current use are capable of penetrating significant thicknesses of metal plate without great stress, damage or destruction to equipment and passage of significant or undesirable duration of time in rock drilling. In existing technology, rock drilling equipment is removed from a hole and specific equipment is substituted or exchanged to address drilling through different materials such as a plate, rebar, etc. Existing approaches have drawbacks, not the least of which is a need to stop rock drilling and the time and logistics associated with exchanging or substituting equipment and then replacing and resuming rock drilling once the dissimilar material, e.g., inorganic obstacle, is overcome.
Hammer-drill equipment can be used with rock drilling relying on a combination of low-rpm torsional moment and a repetitive axial force to penetrate a target material. The repetitive axial force is known as a “hammer feature” as its effect is the same as a hammer striking the end of a masonry chisel. As the name suggests, drills with this feature often achieve this effect by employing an internal hammer to strike an end of an inserted masonry bit. Typically, a masonry bit is a form of twist bit milled from relatively soft steel with a hardened chisel point braised onto the bit's end forming the cutting edges. The hammering motion breaks up the rock at the point of contact between the chisel point and the material being drilled, while the rotating flutes remove the resultant debris. For “heavy duty” hammer drills, such as those employing the Slotted Drive System (SDS) Max form factor bits, the hammer feature is always activated and cannot be disabled by the user.
Drill equipment associated with drilling into metal relies primarily on the torsional moment applied to the drill bit to employ the bit's geometry and achieve a desired cutting action, while the axial force primarily keeps the bit in contact with the target material. The cutting action is the result of the bit's cutting edge being rotated while in contact with the surface being drilled. If such a bit is employed in a drill with the hammer function active while attempting to drill through metal, the bit will rebound from the hardened surface with each blow of the hammer. This will prevent the engagement of the cutting edge with the surface and the loss of contact will result in the inability to penetrate the hardened material.
Existing steel cutting bits are not designed to be employed in a drill with an active hammer feature, cut large diameter holes, or to routinely encounter rock surfaces without rapidly dulling. Employing alternate means to penetrate the material so that drilling may resume, have certain drawbacks making their employment undesirable. Cutting torches require fuels, expendable rods or both and leave hot residue in the path of the drilling equipment. Falling slag is a safety hazard associated with some types of existing approaches. Torches and energetic/explosive systems cannot be used in all environments or scenarios. These restrictions are especially likely to be encountered underground or indoors.
Hammer-drilling equipment may be especially adapted for industrial or fixed site operations and the use of a specialized bit for penetrating the inorganic obstacle allows the continued use of the safer equipment. Improved bits allow for drilling of holes in metal with hammer-drilling equipment even if the hammer function cannot be disabled. An exemplary bit can be designed to cut steel and other metal at low revolutions per minute (RPM) while allowing for some contact with the rock surface behind the steel without rapidly destroying the tool or negatively affecting the drill's hammer function. Use of this exemplary bit during rock drilling allows the drilling to progress through steel and similar materials when encountered by simply changing the bit. Equipment can remain in place and torches and exothermic/energetic systems are no longer required with embodiments of the invention. Exemplary aspects of the invention can also reduce time associated with drilling through mixed materials and reduces the amount and types of equipment currently necessary to accomplish this task. These bits are designed for use on the surface or inside the bore hole.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.